DESCRIPTION (Verbatim from the Applicant's Abstract): The overall goal of this project is improved radiotherapy treatment of patients with cervical cancer with use of positron emission tomography (PET). PET with F-18 fluorodeoxyglucose (FDG) will be used to provide three-dimensional definition of the primary tumor volume and regional spread of disease to more accurately administer brachytherapy. PET-based prognostic indicators will be developed. The first step will be verification of the ability of PET to accurately define tumor volume and to differentiate recurrent tumor from radiation-induced inflammation. Tumor size and extent of disease will be correlated with the results of magnetic resonance imaging in patients receiving radiotherapy with evaluation of FDG uptake before, during and after radiotherapy. Techniques will be developed to accurately determine the position of the brachytherapy applicator in relation to the tumor volume. FDG-PET images showing the primary tumor and regional spread of disease will-be spatially registered with the position of the brachytherapy applicator after placement of the applicator in the patient, thus permitting modification of the source loading in the future to optimize the dose to the tumor while minimizing radiation of the adjacent normal structures. The dose to the tumor and normal structures will be evaluated and follow-up will be performed to assess the rate of recurrence and complications in relation to the calculated doses the patients actually received. The potential impact of PET-guided alterations in source loading and treatment duration will be evaluated. To determine the prognostic value of PET, the volume of the primary tumor and the tracer uptake and heterogeneity of uptake within the tumor, obtained from FDG-PET images, will be correlated with the rate of tumor recurrence to determine PET markers that will identify patients at high risk for early recurrence who may need more aggressive initial treatment.